2.5 weeks ago I brewed what was supposed to be a 1.100 OG ale (June Zymurgy Lagunitas Brown Shugga' clone). My 60 minute mash was 2o under, @ 153o instead of 155o. I used a stir plate and pitched a 1800mL starter, per Mr. Malty, at 59o, and have slowly been warming it up since then. It's currently up to 66.

My issue is I've been stuck at 1.040 for about 5 days now. I added some yeast nutrient and roused the cake twice. I'm probably answering my own question, but could being 2o under lead to such a difference in readily available sugars that my FG could end up being so high? Should I raise the temp to the low 70's?

Your yeast was in the low 60's for 2.5 weeks? raising it to about 68 degrees would allow the yeast to be more active, therefore, lowering your attenuation. But it has been a while since you pitched. If that were my situation I would pitch a new starter. A fewer amount of yeast cells though

Not sure where that guy is supposed to end up, but you may have a combination of issues here - big beer overstressed yeast; less fermentable wort than expected; dormant/shocked yeast. But the starter should have been pretty close to what is needed at 1800ml, the mash temp is not out of line at that temperature and I can't imagine the yeast was shocked at 59F. Is there a possibility that the temperatures are inaccurate? I would raise it up at this point and see what happens. Then perhaps try a hardy yeast strain addition to see if it can metabolize it further.

good luck and post what you do and what happens - I am curious to know.

Adding some safale 05 was on the top of my list of fixes. I should have prefaced that my fermentation chamber is a big square igloo cooler filled with ice packs and water, so while the water temp outside the carboy started at 59, the internal temp was probably closer to 65 once fermentation started. I even mixed the grains for 10 minutes because the grain bill was so large (22.5 lbs). I'll pitch some more yeast and will let you know what happens.

This is also the third time this has happened to me in the past year or so, esp for my bigger brews, so perhaps my thermometer is el cheapo and it's time to get a new one.

What you guys are all missing is that WLP002 is a very quick flocculating yeast. You may only need to rouse the yeast on the bottom to get it started again. The Burton Union system was designed to keep this strain in suspension - it loves to clump together and drop out. Try rousing, if that doesn't work a fresh slurry should work.

rousing wlp002 can be a big pain in the butt. Major, having a conical can probably do it with co2 injected through the bottom valve which might actually work. In my experience short of adding fresh wort you can't really get this yeast to un-floc by any reasonable means at home. I vote for trying to add a big bump of fresh yeast.

To the OP, if you want to know how much potential for attenuation you have left, take a sample (8-10 floz) and add a whole tube of WLP002 and treat it like a starter. Shake it to aerate. keep it really warm, do everything you can to make the yeast happy instead of trying to make good beer. give it a few days and take a reading on that. That should be pretty close to your true floor on this beer. Then you will at least know for sure that you can get it to go lower or not.